Conventional very small aperture terminal (VSAT) antennas utilize a fixed polarization that is generally hardware dependant. The fixed polarization is because an antenna is typically configured to pass one polarization, such as left-hand circular polarization (LHCP), and reject the other polarization, such as right-hand circular polarization (RHCP). Types of polarization include elliptical, circular (RHCP and LHCP), and linear polarization (vertical polarization and horizontal polarization). During installation of the satellite terminal, the basis polarization is generally set and the polarizer is fixed in position. Changing this setting generally requires a technician at the terminal to physically manipulate the polarizer.
Unlike a typical single polarization antenna, some devices are configured to change polarizations without disassembling the antenna terminal. As an example and with reference to FIG. 1, a prior embodiment is the use of “baseball” switches 101 to provide electronically commandable switching between polarizations. As can be understood by the block diagram, the rotation of the “baseball” switches 101, by connecting one signal path and terminating the other signal path, cause a change in polarization. A separate rotational actuator with independent control circuitry is generally required for each “baseball” switch 101, which increases the cost of device.
Furthermore, a prior art solenoid switch is another typical device that may be used to provide electronically commandable switching between polarizations. A typical solenoid switch comprises a coil wrapped around a magnetic core, which can be controlled to move back and forth through the coil. The moving core is designed to strike various contacts, and the position of the core is maintained using various mechanisms. One mechanism example is the use of a spring to exert force on the core in a first direction, which is counter to the force and direction generated by the core once the coil is energized. The spring is extended when the switch is energized, and then recoils back into position when power is cut (i.e., the magnetic force is off). Furthermore, a spring-aided switch has reduced force since the force of the spring acts in the opposite direction of the magnetic force. The primary drawback of spring-assisted solenoid is that the switch must remain energized to stay latched. The continuous power may be unachievable or undesirable in various applications.
A second prior art design is the use of two separate solenoids to generate bidirectional motion. However, the use of two solenoids has increased costs and increases the complexity during assembly. Other drawbacks of typical solenoids include limited travel range and maxim force over a narrow range. In general, the force exerted by a typical solenoid increases until the end of traveled distance in nonlinear fashion. The nonlinear force results in a narrow operation window if greater force is desired for longer ranges of travel. The solenoid typically has one end enclosed with magnetically permeable material to increase force. However, the core's range of motion is limited by the enclosed end. Although complex multiplying linkages and auxiliary assemblies may be used to overcome this limited range, the increased cost can be substantial along with added system complexity.
Thus, there is a need for a new low cost method and device for solenoid switching that results in low cost and low complexity system.